1. Field of the Invention
This invention relates to new and useful improvements in systems for permitting the use of elevators during a building fire.
2. Description of the Prior Art
In most elevators lobbies in the United States, there are signs warning against the use of elevators in the event of fire and directing the building occupants to use marked exits stairways. The National Fire Protection Association (NFPA), Life Safety Code lists the following problems involved with the use of elevators as fire exits:
If an elevator call button has been pushed at that level, an automatic elevator may stop automatically at the floor involved in the fire and open automatically, thus exposing occupants to fire and smoke.
A large number of people attempting to crowd into an elevator in case of fire might prevent the doors from closing and make it impossible for the elevator to start.
If electric supply cables are damaged during a fire, the elevators may be rendered inoperative and trap occupants in elevators stopped between floors. There might not be time to permit rescue of trapped occupants through emergency escape hatches or doors.
Persons seeking to escape from a fire by means of a elevator may have to wait at the elevator door for some time, during which they may be exposed to fire, smoke or developing panic.
In most multistory buildings, the elevators are set to descend automatically to the ground floor in the event of fire. Fire fighters have keys to control elevators manually during building evacuation and fire fighting.
Since smoke infiltration into elevator shafts frequently threatens lives and hinders elevator use by fire fighters, it is current practice in some buildings to provide top vents in elevator shafts serving more than three floors to allow the elevator shaft to act as a smoke shaft carrying smoke from the fire floor out of the building. Because of leakage around elevator doors, however, this feature may contribute significantly to smoke movement beyond the fire floor by way of elevator shaft itself.
Several suggestions have been made to permit the utilization of elevators in buildings during fires. The use of elevators may be needed for the evacuation of physically handicapped persons who can not walk down the stairways. The elevators may also be needed for the use of fire protection or fire control personal.
One of the proposals for assisting in the evacuation of buildings is seen in Heba U.S. Pat. No. 3,952,452 which discloses the use of a blower to pressurize stairwells to keep out fire and smoke and to assist in the opening of doors which might otherwise be held shut by a pressurize differential. In Koplon U.S. Pat. No. 3,817,161 a system is shown wherein the elevator shaft or hoistway is pressurized by a blower to keep the shaft free of smoke and reduce the hazard of suffocation. The elevator is also designed for drawing air from the hoistway to discharge into any given floor through the open elevator doors to clear smoke from that level.
ASHRAE journal, April 1984, pp.23-33, discusses at length the problem of smoke control for elevators which need to be used during a fire either for evacuation of building occupants or for use by fire department personnel. Heating-Piping-Air Conditioning, April 1984 includes several articles dealing with smoke control in multistory buildings.
The foregoing references do not suggest the concept of this invention, viz., the continuous pressurizing of an elevator cab to permit its use during a fire for building evacuation or for use by fire department personal.